1. Field of the Invention
The present invention relates to a propylene copolymer and a thermoplastic resin composition. More particularly, the invention relates to a novel propylene copolymer which gives excellent thermoplastic resin composition having outstanding flexibility in mixing with a resin like polypropylene, use of said propylene copolymer as a polyolefin resin modifier, and a thermoplastic resin composition containing said olefin copolymer and polyolefin resin.
2. Description of the Related Art
Polypropylene resin has been used for various ends widely as a resin having excellent properties in stiffness, thermal deformation temperature, surface hardness, etc. but it has defects in impact resistance and flexibility. As a method for improving these defects, the procedures to blend the polypropylene resin with a low-crystalline ethylene-.alpha.-olefin copolymer such as ethylene-propylene copolymer, ethylene-1-butene copolymer are well known. Japanese Patent KOKAI Publication No. 98095/1993 discloses that a thermoplastic resin composition made by blending a specific ethylene-propylene-1-butene copolymer with the polypropylene resin along with an inorganic filler has excellent impact resistance and surface hardness.
On the other hand, the propylene copolymer obtained by copolymerizing propylene with ethylene or .alpha.-olefin by using a solid state titanium catalyst has excellent transparency, impact resistance, heat sealing property, etc. which cannot be attained by homopolypropylene. Such a copolymer is extensively used for automobile material, construction material, industrial material, cable material, polyolefin modifying material, packaging film, etc. Among them, as the modifying material especially for polyolefin resin, the demands for improving flexibility, impact resistance and heat sealing property of polypropylene have been particularly increasing. However, with the conventional propylene copolymer or polyolefin material modifying with the propylene copolymer, there has been the effects of the composition distribution of the propylene copolymers and said materials did not necessarily reach the required levels in flexibility and transparency. In Japanese Patent KOKAI Publication No. 12635/1997 there is disclosed a propylene-1-buten-ethylene copolymer obtained by using a specific metallocene catalyst. Since said propylene-1-buten-ethylene copolymers have narrow molecular weight distribution and contain 1-butene and ethylene in specific proportions, said copolymer has excellent transparency, stiffness, heat sealing property, impact absorbing property, and can be the suitable materials as a modifier for resin. In Japanese Patent KOKAI Publication No. 301934/1996 also there is disclosed a propylene-ethylene-.alpha.-olefin copolymer obtained by using a metallocene catalyst, and there is disclosed that these propylene-ethylene-.alpha.-olefin copolymers have narrow molecular weight distribution and composition distribution, and have excellent strength and low permanent elongation, and good transparency in comparison with the conventional propylene-ethylene-.alpha.-olefin olefin copolymers obtained by the solid state titanium catalysts because they contain ethylene and .alpha.-olefin in specific proportions. Said copolymers can be the polyolefin materials having excellent heat resistance as the modifying materials for polyolefin resin.
However, in recent years, even in the field in which the soft vinyl chloride resin and the like were used, demands for using a polyolefin material have come to be enlarged. In such uses, the higher performances are required in the aspects of flexibility, heat resistance, scratch resistance, transparency, etc. In the procedures of blending the polypropylene resin with a low crystalline ethylene-.alpha.-olefin copolymer, or propylene copolymers obtained by using the solid state titanium catalyst, or the polyolefin materials using the propylene copolymers disclosed in Japanese Patent KOKAI publications No. 12635/1997 and No. 301934/1996 and polyolefin materials using said propylene copolymers as a modifier, said materials have not necessarily satisfied the required levels.
The present inventors have intensively studied on the propylene copolymers, and have found that the materials having excellent flexibility can be obtained by using the propylene copolymers obtained by using a specific metallocene catalyst as a modifier.